STRUCTURE, DIELECTRIC-RELAXATION AND ELECTRICAL-CONDUCTIVITY OF ANTHRENE-2,3-DICHLORO-5,6-DICYANO-1,4-BENZOQUINONE 1 1 CHARGE-TRANSFER COMPLEXES/

2,3,7,8-Tetramethoxychalcogenanthrenes (5,10-chalcogena-cyclo-diveratr ylenes, 'Vn(2)E(2)', E = S, Se) form isotypical 1:1 charge-transfer (C T) complexes with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). X-r ay analysis of Vn(2)S(2) . DDQ shows the compound to have a columnar s tructure with segregated stacks of donors and acceptors. The donors ar e virtually planar in accordance with a formulation of [Vn(2)E(2)](+)[ DDQ](-). Donor cations and acceptor anions are equidistant in their re spective stacks, but in each case they inclined to the stacking axis, nevertheless guaranteeing an optimum overlap of the half-filled fronti er orbitals which are of pi-type character according to MNDO calculati ons. Dielectric ac measurements of permittivity epsilon' and loss fact or E '' clearly reveal two processes, a dielectric one at low temperat ures and a conductive one at high temperatures. The dielectric process can be described by the Havriliak-Negami (HN) and the Kohlrausch-Will iams-Watts (KWW) model, and the conductive process by a Debye-type plo t. Using these methods, the relevant parameters are evaluated. The de conductivities of polycrystalline samples moulded at 10(8) Pa show a t emperature dependence in the plots of ln sigma vs. T-1, which is typic al of semiconductors. Two slopes are found; that in the low-temperatur e region (<285 K) is explained by an easy-path model (intragrain condu ctivity with low activation energies), whereas in the high-temperature region conduction across the grain boundaries (with higher activation energies) is becoming predominant. The activation energies for the in trinsic conductivities obtained by the ac and de measurements are simi lar. Despite the columnar structure with segregated stacks, due to sto ichiometric oxidation states of the components, the absolute values of conductivity are low ten. 10(-6) S cm(-1) at 293 K), though higher (b y a factor of ca. 10(3)) than those of compounds like Vn(2)E(2) . TCNQ with stacks in which donor and acceptor molecules alternate.